Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$43.25	4.745%	$45.3022	$45.30	$45.30	$45.30
Purchase #2	$63.57	6.152%	$67.4808	$67.48	$67.50	$67.50
Purchase #3	$217.59	10.722%	$240.92	$240.92	$240.90	$240.90
Purchase #4	$70.36	6.403%	$74.8652	$74.87	$74.85	$74.90
Purchase #5	$27.74	5.771%	$29.3409	$29.34	$29.35	$29.30
Purchase #6	$71.99	8.459%	$78.0796	$78.08	$78.10	$78.10
Purchase #7	$161.28	13.834%	$183.5915	$183.59	$183.60	$183.60
7 purchase totals =	$655.78		$719.5802	$719.58	$719.60	$719.60